In recent years, with automobiles achieving higher functionality, devices have been increasing that detect a step-on amount or rotation angle of, for example, a brake pedal using various types of rotation angle detecting devices and switches to perform various types of control on a vehicle.
FIG. 20 is a perspective view of conventional rotation angle detecting device 5.
Rotation angle detecting device 5 includes case 1 and rotating body 2.
Case 1, substantially box-shaped made of an insulating resin, contains rotating body 2 rotatably. One end of rotating body 2 is provided thereon with lever 2A projecting outward from the side opening of case 1.
The inner wall of case 1 and rotating body 2 have a coiled spring attached therebetween in a slightly deformed state. The spring presses rotating body 2 to a predetermined angle to retain lever 2A in place.
Rotating body 2 has a magnet attached thereto, and a magnetism detection element (e.g. a Hall effect sensor) is disposed facing the magnet with a predetermined clearance from the magnet.
FIG. 21 is a perspective view of conventional push switch 10.
Push switch 10 includes case 6 and actuator 7.
Case 6, substantially box-shaped made of an insulating resin contains actuator 7 movably up and down, and operation shaft 7A on the top end of actuator 7 projects upward from the top surface of case 6.
The inner bottom surface of case 6 and the bottom end of actuator 7 have a coiled spring attached therebetween in a slightly deformed state. The spring presses actuator 7 upward.
A fixed contact implanted in case 6 faces a movable contact made of a conductive metal, attached to actuator 7 in case 6. The movable contact and the fixed contact form a switch contact.
As shown in FIG. 22, rotation angle detecting device 5 is attached to arm 31A near the rotation shaft of automobile brake pedal 31. The magnetism detection element of rotation angle detecting device 5 is connected to, for example, an electronic circuit on the vehicle with lead wires and connectors.
Push switch 10 is attached in front of brake pedal 31 with operation shaft 7A pressed by arm 31A. The switch contact of push switch 10 is connected to a stop lamp and such as an electronic circuit on the vehicle with lead wires and connectors.
In a state where brake pedal 31 is not being depressed and brake pedal 31 is being supported frontward by push rod 33 projecting from the inside of cylinder body 32, actuator 7 of push switch 10 is pressed with the spring being deformed, which causes the movable contact to be separated from the fixed contact, resulting in the switch contact being electrically disconnected. Consequently the stop lamp is off.
When brake pedal 31 is depressed, arm 31A rotates to be separated from the front end of operation shaft 7A of push switch 10, thereby removing the pressing force. Consequently, the elastic return force of the spring causes actuator 7 to move to its original position. The movable contact contacts the fixed contact to make the switch contact in an electrically connected state, thereby lighting the stop lamp.
Rotation of brake pedal 31 causes lever 2A of rotation angle detecting device 5 to swing and rotating body 2 rotates with the spring being deformed, and thus the magnet attached to rotating body 2 rotates as well, which changes the direction of a magnetic field flowing from the magnet to the magnetism detection element opposite to the magnet.
The magnetism detection element detects strength and weakness of magnetism produced by the change of the direction of the magnetic field. According to an angle signal output from the magnetism detection element, the electronic circuit on the vehicle calculates a rotation angle of rotating body 2, namely a step-on amount of brake pedal 31, for various types of control on the vehicle according to the step-on amount.
To sum up, applying brake pedal 31 causes actuator 7 of push switch 10 to move up and down, thereby electrically contacting and breaking the switch contact. This operation turns the stop lamp on and off and rotates rotating body 2 and the magnet of rotation angle detecting device 5. Then, the electronic circuit detects a rotation angle of rotating body 2, namely a step-on amount of brake pedal 31, based upon a change of magnetism detected by the magnetism detection element, for performing various types of control on the vehicle.
A rotation angle detecting device similar to conventional rotation angle detecting device 5 is disclosed in US Patent Application No. 2001/0009366A1.